Indeed, the Uygurs are Turkic people and there might indeed be some similiarity to a Southern European. Also, the photograph on the passport used needs not be the original one.
That said, if (and this is a big IF!) there should indeed be a criminal act involving the person in question connected to this accident, it is a bit illogical to use an airline of a fellow Muslim country for this attack, as despite the large number of Chinese nationals on the passenger list, it is nevertheless a Malaysian aircraft and the attack will rather be seen as directed towards Malaysia than China. Also, criminals in the past have tended to proudly and quickly claim responsibility for such an attack; as far as I know such word is still not out on this accident.
Not even a part of the aircraft (apart from some oil that may or may not be related to this accident) has been found yet, and already the accident is solved by many, it seems. Please be not too quick to jump to conclusions.